312 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
irrigation has been studied, and all the large streams with most of the minor ones 
have been gauged at proper intervals throughout the year, giving a fair approxima- 
tion to the amount of water wbieh may be calculated upon. The work of Mr. Hall 
forms an admirable basis upon which to commence a well-devised system of irrigation 
fdr this area. 
As to the tolal amount of land which can be reclaimed by means of irrigation, but 
the merest estimates can be made. It is, as was shown above, almost purely a ques- 
tion of the amount of water available. In the first place, we have but few measure- 
ments of the capacities of streams; and, except in the case of California, they are but 
single measurements, and simply represent the state of the stream at the time of gaug- 
ing. The next day, or the day before, the stream may have carried a very different 
amount of water. In California, as w as stated above, a number of streams have been 
gauged at short intervals throughout one year. From these measurements with the 
areas of the drainage basins, it may be possible to make rough estimates of the capaci- 
ties of the streams of other parts of the country. 
But there are other factors entering to complicate the subject. The first, and most 
important, is the question, What is the "duty " of water, i. €., the amount required to 
irrigate a unit of land, or the number of acres which one cubic foot per second, 
throughout the season, can serve f This is not a fixed quantity, but (lifters with dif- 
ferent crops, with different soils, and a variety of other circumstances. Corn requires 
less water than almost any other crop, while oats and grass require the most. Clayey 
lands need less than sandy soils, for very obvious reasons. Very level land requires 
more water than sloping land, as it absorbs more while under irrigation. Crops 
which are sown broadcast, like wheat or oats, require more water than those planted 
in drills, as the more expensive mode of flooding must be resorted to for irrigating 
them. Early sown or planted crops require less water fhan those planted late, as 
there is more rainfall in the early part of the season, and evaporation is not as rapid. 
Land that has been irrigated requires less water than new land. The reason proba- 
bly is that the soil and subsoil become thoroughly soaked in time, Some even go so 
far as to say that a piece of land, after being irrigated for a number of years, requires 
no further watering. It is possible that this may be true for a season or two, but as 
soon as the water disappears from the subsoil, irrigation will again be necessary. 
Major Powell, in his able report on " Lands of the Arid Region. - ' states that the prac- 
tice in Utah allows from 80 to 100 acres to the cubic foot per second, which is as high 
a duty as would be expected in Utah, where irrigation is not carried on intelligently 
or economically. In the San Joaquin Valley, of California, where irrigation is car- 
ried on by Americans, and where there is an abundance of water, we naturally find a 
very low duty, ranging from 50 to 150 acres per second-foot. In the counties of Los 
Angeles and San Bernardino, however, where most of the ranchmen are Mexicans, who 
have practiced irrigatioii for centuries, and where there is a great scarcity of water, 
nearly all the streams and springs being used up to their full capacity, we find the 
duty ranging from 300 to 1,500 acres per second-foot. To account for this difference 
between two sections of the State, Mr. Hall writes as follows : " The explanation un- 
doubtedly lies in the greater experience acquired by the irrigating communities of Los 
Angeles and San Bernardino Counties, where the art has been practiced longer than in 
other parts of the State, resulting in the acquirement of more skill in the use of water ; 
in the measures which nature has compelled the irrigators to take for the conservation 
and economical distribution of water, and to tome extent to the character of the crops 
produced, * * * and last, though by no means least, we find in Los Angeles and 
San Bernardino Counties better irrigation organizations than in the San Joaquin Val- 
ley, which tends to harmonize interests and prevent waste." 
A few statistics from the practice in foreign countries will be instructive in this con- 
nection. In Algeria the average duty for cereals is reported as 420 acres per second- 
foot. In the sub-Himalayan districts of India, the practice is to allow one second- 
foot for 218 acres. In Granada cereals and vines are irrigated at the rate of '-'40 acres 
